HEY. R. ABB AT ON HBMILEIA YASTATRIX. 173 



Observations on Ilemileia vastatrix, the so-called Coffee-leaf 



Disease. By the Rev. K. AbiKt, M.A., F.O.S., Fellow 

 of Wadham College, Oxford. (Communicated by W. T. 



Thiselton Dyer, M.A., F.L.S.) 



[Bead June 6, 1878.] 

 (Plates XIIL-XIV.) 



Historical Remarks. — One of the greatest scourges which the 

 coffee enterprise of Southern India and Ceylon has had to con- 

 tend with is, without doubt, Hemileia vastatrix, or the so-called 

 Coffee-leaf disease. Appearing first on a new estate in Madul- 

 sima, a district in the south-eastern corner of the mountain-zone 

 of Ceylon and bordering on the Low Country, it spread with re- 

 markable rapidity over the various coffee-districts, attacking both 

 old and young trees with almost equal severity. At first the 

 " disease " was regarded by those best able to judge as a temporary 

 one, which would run its course for a year or two, and then dis- 

 appear as mysteriously as it came. This view was strengthened 

 by the apparent departure of the pest when the rainy monsoon 

 came on ; but with the return of dry weather it reappeared. 

 The effect of the disease presently became apparent in a diminu- 

 tion of the fruit which the tree yielded ; and in 1872 the matter 

 was recognized as serious. Previous to and including 1871 the 



o 



average yield for five years over the whole' island had been 

 4*5 cwt. per acre ; whilst for the five succeeding years the average 

 has only been 2*9 cwt. — a decrease in the production of somewhat 

 more than one third. A portion of this decrease is believed to 

 have been due to exceptionally unfavourable seasons for the blos- 

 soming and development of the fruit. 



The following is an approximate list, showing the number of 

 acres in cultivation, the total production of coffee, and the yield 

 per acre during the three-year periods from the year 1866 up to 

 the present time, 1867, 1870, 1873, and 1876 being the middle 

 years of each period : — 



Acreage. Production. Yield per 



I860) cwt. acre. 



1867 \ 170,000 728,440 4*28 

 18G8J 



I860 ) 



1870 1 18G,000 845,375 454 



1871) 



LINN. JOUUN. — BOTANY, YOL. XYIT. * 



